1. Technical Field
The present disclosure relates to a transmission device of a powered tool, such as an electronic wrench or an air powered wrench, and more particularly to an impact device for power transmission.
2. Description of Related Art
Many of commercially available electronic wrenches or air powered wrenches are equipped with impact devices for power transmission therein. The impact device for power transmission is adapted to be connected with a rotation shaft of a motor mounted inside the wrench and usually composed of an output shaft and an impact mechanism. By means of the impact mechanism, the output shaft is indirectly driven by the motor to rotate to lock or loose a screw nut or bolt. While the screw nut or the bolt is locked to a certain degree which results in the output shaft hard to be further driven to rotate, the impact mechanism, which is continuously driven by the motor, will intermittently impact the output shaft to make the output shaft rotate with great torque at the instant that the output shaft receives the impact, enabling the initially locked bolt or screw nut to be locked more tightly or the tightly locked bolt or screw nut to be loosed correspondingly.
U.S. Pat. No. 5,704,434 disclosed a hydraulic torque pulse mechanism. The mechanism is a kind of impact device for power transmission by utilizing hydraulic pressure, such as oil pressure, to generate torque. This mechanism has not only power transmission function and impact function, but also advantages of low vibration and low noise due to characteristic of hydraulic pressure.
However, because of structural limitation, the hydraulic pressure of the conventional impact device utilizing the hydraulic pressure to generate torque is not adjustable, such that the conventional impact device can only output torque of a fixed value. In other words, the output torque of the conventional impact device cannot be adjusted subject to the user's demand.